This is what I could squeeze out of my R9 290(X)s:
The slots of a 990FX board are populated as follows:
Gigabyte 290X (I forgot to check the RAM type) 16x 2.0 PCI-E lines
ASUS 290 (Elpida RAM) 4x 2.0 PCI-E lines
ASUS 290X (Hynix RAM) 16x 2.0 PCI-E lines
ASUS 290 (Elpida RAM) 4x 2.0 PCI-E lines
ASUS 290 (Hynix RAM) 1x 2.0 PCI-E lines
I still have an empty 1x 2.0 PCI-E slot and I guess my 2kW 12V PSU (plus a 750W ATX PSU) could handle the load but I am not sure if I should buy another 290 since the prices went up.
I installed the latest BIOS version from MSI a few days ago on all cards. This made zero difference for me.
OS: Xubuntu 13.10 AMD64 (I am planning a switch to Debian 8.0 test version)
CPU: Athlon XII 255 (stock) - I think I should upgrade it for a Bulldozer chip for their better power saving features and/or some small scale XPM mining on the sideline
RAM: 4Gb 1600Mzh Corsair (I couldn't pick up a 2Gb stick for significantly cheaper, so I used this, even though it's overkill)
cgminer: original 3.7.2 built from source with SDK 2.9 and ADL 6.0 (-Ofast)
My settings:
"intensity" : "20,20,20,20,20",
"thread-concurrency" : "36044,36044,36044,36044,36044",
"lookup-gap" : "2,2,2,2,2",
"gpu-threads" : "1",
"worksize" : "512,512,512,512,512",
"gpu-powertune" : "50,50,50,50,50",
"gpu-engine" : "920,1010,1015,1000,1080",
"gpu-memclock" : "1500,1500,1500,1500,1500",
"gpu-fan" : "40-100,40-100,40-100,40-100,40-100",
"temp-cutoff" : "99,99,99,99,99",
"temp-overheat" : "95,95,95,95,95",
"temp-target" : "85,85,85,85,85",
"temp-hysteresis" : "1",
"auto-fan" : true,
My hash rates:
I think somebody should really take a look at the scrypt code and optimize it a little bit more for the new drivers and SDKs to squeeze out a little bit more from these cards.